


she shimmers like the sea (when the sun shines)

by gallantrejoinder



Category: Doctor Who
Genre: Alternate Universe - Fairy Tale, Alternate Universe - The Little Mermaid Fusion, F/F, Magic, True Love's Kiss, gay mermaids, the ocean
Language: English
Status: Completed
Published: 2017-07-19
Updated: 2018-04-18
Packaged: 2018-12-04 05:52:52
Rating: General Audiences
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 3
Words: 6,830
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/11548842
Author URL: https://archiveofourown.org/users/gallantrejoinder/pseuds/gallantrejoinder
Summary: Heather has always been fascinated with humans, to the disapproval of other merfolk. But when she rescues a sailor named Bill Potts from drowning, she discovers that she's willing to do anything to walk amongst humanity.





	1. Chapter 1

They call her Heather, after a flower from the world of humanity. From the beginning, she is not like the other merfolk, and they will say for years afterwards that she was cursed to have such a name. Destined for tragedy – fated to lose everything to humans and their greedy hands.

Perhaps they are right. But that does not stop Heather from dreaming about the world above the ocean.

She collects trinkets, small objects, and bits and pieces of nothing that drift down to her watery underworld. She doesn’t always know their purpose – is this for hair? Could this be used to swim? How do they eat with these? – But she knows they must be wonderful, for they are so strange and fascinating to behold.

The other merfolk do not like it. They will not listen, when she tries to explain – to show them that the wonders of the world of humanity are beautiful. They mutter that it is not right for a mermaid to hold such a fascination as she does, and she learns to hide her precious things away, keeping them far from prying and judgemental eyes.

 _Stay away from the shorelines, Heather. Humanity cannot be trusted, Heather_. And most important of all – _You cannot_ ever _be seen by a human, Heather. They would kill you, for envy of your beauty_.

But she cannot help herself – she dreams of the world above, the place where people walk upon sturdy legs, and sail over her world, oblivious to her longing below. She always swims more closely to the shipping channels than she should, watching them fly over her, sometimes daring to swim close enough that she can hear their voices, and peep in through portholes at their faces.

It’s what she does on the night she meets Bill Potts.

The ship is close – too close – to the rocky shore. It’s a stormy night, and even Heather, with her strong tail, can barely manage to keep herself upright in the tumultuous waves. She surfaces, her head instantly lashed with rain, and rises through the air on a wave bearing down on the ship. She watches, silently, as the crew struggle with the ropes. There are orders being shouted back and forth – Heather can see two men at the wheel, battling for control against the elements.

But it’s the girl her eyes are pulled to – with a soaking wet mop of curly hair, and a pale blue jacket to shield her against the rain standing out against the dark wood. She’s holding on to a rope, but her feet are slipping – in a flash of lightning, the girl screams, and the ship is thrown to the side –

And she falls, limbs flailing, into the water.

Heather hears someone cry out – _Bill! No!_ – but no more, as she dives below the surface, unthinking, knowing only that she needs to rescue the girl.

She swims as fast as her tail can push her, looking around wildly, her hair floating around her head in a cloud that obscures her vision. But it’s not long before lightning illuminates the roiling waves once more, and Heather sees the silhouette of the girl – Bill – floating in the water, unmoving.

Heather races towards her and takes Bill in her arms in mere seconds. In a few moments more, she reaches the surface, still carrying Bill’s weight in her arms. Once there, over the thunder and roaring of the waves, Heather listens carefully (so carefully, her heart pounding with fear,) for Bill’s breath. And, thanking the stars above, Heather hears it.

The next hour is the most strenuous of Heather’s life. She spends it swimming towards the shore, Bill in tow. It is immeasurably difficult, and Heather’s muscles scream with protest – but the storm clears, slowly, and then all at once. Before she knows it, Heather is exhaustedly falling upon soft, white sand, the beach stretching out before her, and the sun shining weakly through the clouds.

She’s never been so close to the human world before. Even she had never dared come so close.

Bill lies, motionless, upon the sand. Her breathing is steady, yet shallow. There’s a wound on her head that Heather does not know how to treat. She knows nothing of human medicine.

In lieu of treatment, she hums a song, quietly, leaning over Bill’s still form. It is the kind of song the healers sing down below, when one of their own is wounded. The kind of song that is sung to children, to let them know the world isn’t ending. That the ocean is still there to hold them.

Slowly, but surely, Bill’s eyes begin to open. Her gaze is unfocused at first, a tiny frown appearing between her eyebrows as she takes in her surroundings. Her eyes settle on Heather, who stops singing, smiling softly at her.

“Bill,” she whispers.

“Am I dead?” Bill’s voice is hoarse, yet quiet.

Heather shakes her head. She wants to say something – wants to make Bill stay with her, tell her about the human world. She wants Bill to keep looking at her like this, with wonder in her eyes.

“Who are you?” Bill says, and with a start, Heather is reminded that _she cannot be seen_.

The jolt of fear must make itself known in her features, because Bill suddenly reaches for her, taking the arm that is leaning over her prone body.

“Don’t go,” she pleads, but Heather shakes her head, afraid.

And without another word, she slips back into the waves and swims far, far away from the world of humanity. From the world that holds Bill in it.

 

~

 

Heather cannot so easily forget the glimpse she was given into the human world. She drifts through the merfolk lands, listless, thinking of Bill. The wonder in her eyes, so dark, and so thrillingly intoxicating.

Heather lasts two days before she finds herself swimming towards the forbidden lands. The place where the ocean awakens, and whispers secrets into the ears of human and merfolk alike, luring them towards their doom.

 _Heather, Heather, Heather_ , they sing. _Lonely, lonely, lonely_ , as she swims ever deeper into the canyons and trenches.

But the living ocean is not only capable of horror – the magic in the forbidden lands can give Heather a chance to see Bill again. It can make her walk with human legs upon human lands, and learn all there is to know of the world above. No other merfolk can give her what the living ocean can.

She slows her pace only when the voices become insistent, demanding her attention.

 _We can fix it, Heather. We can fix you_. _Fix you, fix you, fix you_.

“I want to go above,” Heather says, boldly, though her heart is afraid. “I want to walk amongst humanity. Will you grant me this?”

The voices laugh, a grating sound that hurts her ears. She betrays no fear.

 _Easy, easy_ , they say. _But there is a price_.

“Name it.”

_You will not speak a word that is not spoken first to you. You will become an echo, like us, Heather._

_Heather, Heather._

She considers it, the possibilities. Surely – surely, she will be able to find a way.

“Have you any other conditions?”

_Yes, yes, yes._

_You must discover true love’s kiss before the year is finished – or be cursed to join us._

_Join us, join us._

A shiver of fear runs down Heather’s spine. To become no more than a cursed voice, echoing forever in the forbidden lands …

But then she remembers Bill’s eyes.

“I accept,” she murmurs, before she can convince herself not to.

And the voices are laughing, laughing, the sound growing louder and louder until Heather claps her hands over her ears, trying to swim away – yet finding she cannot, for her tail is splitting in two, the pain beyond comprehension. She screams, and knows no more.


	2. Chapter 2

She awakens on a beach, and knows in an instant that she is no longer as she was.

Her legs ache – legs she cannot fathom how to use. She stretches out her awareness, feeling the sand underneath her thighs, the light pressure of it. She waits, a cold slap from the waves tickles her soles. She wiggles her toes experimentally, and finds them responsible – it’s not so different from flicking her fins, really. Still, though, her newborn legs ache, and she is reluctant to try standing upon them, afraid they’ll dissolve back into scales the second she tries.

“Hello? Are you all right?”

Heather sits up, quickly, balancing on a reshaped pelvis with a surprising amount of ease. Scanning the horizon, she finally spots a figure in the distance along the beach, calling out to her. Heather opens her mouth to reply, but –

“ _Are you all right_?”

All that comes out is an echo of the stranger’s words. Heather presses a hand to her throat, heart pounding, trying to understand why she said that. It dawns on her, the memory of the echoes in the forbidden lands. They had promised her legs in return for her voice, the ability to make words her own. They have made her an echo, like them.

The figure comes closer, and Heather moves, slowly, to stand. Her legs shake a little, but hold her up. She shivers, the cold air hitting more of her wet skin.

Finally, the figure is close enough to see – and Heather cannot help but smile softly when she realises it is Bill, because of course it is. The echoes could not have left her anywhere else.

“Oh, my god,” Bill says, as she comes close enough to see Heather’s nudity. Bill’s eyes widen, but Heather feels no shame. She is aware that humans wear clothing in their everyday lives, but she has never done so beneath the waves. Besides which, she is proud of her new legs. She does not want to hide them just yet.

“Erm, here,” Bill says, jogging the last few steps towards Heather and shrugging off her outer overcoat. She wraps it around Heather’s shoulders, and the warmth of it makes Heather sigh.

“How did you end up here? God, I can’t believe anyone would leave a girl stranded on a beach without the clothes on her back,” Bill says, sounding concerned.

“ _Clothes on your back_ ,” Heather says, opening her mouth without meaning to. The words simply appear in her throat, without her calling them. She frowns, holding her throat again. How can she be expected to get used to this?

Bill frowns, looking closely at her face. There seems to be a spark of recognition in her eyes, but she hesitates.

“You know, I could swear I’ve seen you before,” Bill says, softly. “But it couldn’t have been you. Unless … Can you talk?”

“ _Can you talk_?” Heather repeats.

“So … limited vocabulary, then,” Bill sighs.

Heather nods vigorously. “ _Limited vocabulary, then_ ,” she agrees.

Bill smiles, a little sadly. “Well. Either way. You’d better come with me – I’ll take you to meet my crew. We’ve a couple of doctors with us – they should be able to help. All right with you?”

“ _All right with you_ ,” Heather echoes, smiling.

That is how their second introduction takes place, and though Heather cannot express the words she wishes she could to tell Bill how grateful she is for her help, how Bill’s curiosity had sparked her own, how Bill had made her brave – Heather is still happy to be wrapped safely in her overcoat, walking on unsteady legs across the beach towards a new life.

 

~

They make it to the inn where Bill is staying with little fanfare, only a few curious glances thrown in their direction at Heather’s bare legs sticking out from Bill’s coat. Bill chuckles nervously and volunteers excuses about Heather’s predilection for early morning swims, and leaves it at that. When they reach the inn, Bill quickly shuffles Heather through to an upper floor, where a long corridor connects several rooms – where, Heather learns, Bill’s crew are staying.

“I’ll take you to the doctors before we do anything else,” Bill says, guiding Heather towards the last door on the left. “Though I’ll have to see if they’ve stopped arguing first.”

She knocks once, and lets herself in without preamble. Inside are two men, sprawled over several chairs – one is old, one is young, one with ferociously powerful eyebrows, and one with none at all, and they are both sound asleep. Bill clears her throat, loudly, and the two of them jolt awake, with eerily similar movements.

“All right, what’s going on?” The younger one grumbles.

“Why are you sleeping in my room again? No, don’t answer that,” the older one says, directing the question at the younger.

“Doctors,” Bill interrupts, clutching at Heather’s arm hopelessly. “You’ve got a patient.”

Both men spring into action, the younger stepping forward to kiss Heather’s cheeks enthusiastically, exclaiming over her paleness, and the older examining her with a critical eye.

“I’m Doctor John Duodecim,” he pronounces. “And this is my assistant, Doctor John Undecim.”

“Assistant? In your dreams,” the younger Doctor Undecim declares. “But never mind all that. What’s your name, eh?”

The last question is directed at Heather, who opens her mouth, once more without thinking.

“ _What’s your name, eh_?” She repeats.

“She does that,” Bill explains. “It’s why I brought her to you two. I wasn’t sure what to do. I found her naked on the beach this morning, and all she seems to be able to say is just … repeating whatever anyone else says.”

The two doctors glance at each other before slowly turning their gaze on Heather. She shrinks into Bill’s side, defensively.

“Have you got a name? Don’t try to answer. Just nod yes or shake your head for no,” Doctor Undecim says.

Heather nods.

“And you don’t know how you came to be on the beach?”

Heather hesitates, unsure of how to explain what has happened to her. She shakes her head, hoping that they will believe she has no memories.

“Hmm,” Doctor Undecim says.

“You’ve an unusual face,” Doctor Duodecim comments. “If I didn’t know better I’d say you came from somewhere with little sunlight … And your skin is dry, too, as if …”

He frowns, deep in thought.

“Best to keep her with us until we know more,” Doctor Duodecim decides.

“Can’t you … I dunno, at least figure out her name, with that freaky mind-trick thing you do?” Bill presses.

Heather blinks, unsure as to what Bill could be referring to. But her questions are quickly answered as Doctor Duodecim walks forward and, without another word, places his hands on the side of Heather’s face, closing his eyes and concentrating. Heather shies away a little at first, but Bill smiles encouragingly at her, so she stays where she is, for the moment. Doctor Undecim is no longer paying any attention, having flopped down on a chair, upside down, with a book.

“A flower?” Doctor Duodecim says, suddenly.

“ _A flower_?” Heather repeats, nodding.

Doctor Duodecim frowns, concentrating still. A few moments pass in silence.

“Heather!” Doctor Duodecim suddenly gasps, opening his eyes suddenly.

Heather nods vigorously. “ _Heather_.”

“Heather,” Bill whispers. The sound of it makes Heather shiver, and she turns to Bill, trying to convey with her eyes alone how thankful she is to be here with her.

“That’s all I’ve got, for now,” Doctor Duodecim sighs. “Set her up in your room. We’re stuck here for the next few months anyway, might as well see if we can train up a new crewmember in the meantime.”

“Oh, yeah,” Bill says, turning to Heather. “Sorry, I didn’t tell you anything. I’m a sailor, y’see, and well … our ship, the Tardis, was wrecked a few weeks ago.”

“Nearly took Bill down with her,” Doctor Duodecim says darkly, and Bill looks uncomfortable.

“Well, I got rescued, luckily. There was a girl … I can’t remember it all that well.”

“That’d be the trauma,” Doctor Undecim chimes in.

“Well, whatever it was, I can’t really remember what happened, other than this girl swimming me to shore. Ran off to find Doctor Duodecim here – he’s my tutor, see – and found the crew at the local inn, toasting to me!”

Heather’s eyes widen as she takes in the tale. She hadn’t thought that Bill’s ship would go down like that, despite the storm …

“And we’ve been here ever since, waiting on repairs to the ship. We’ll be here a while longer, too, so I guess Doctor Duodecim is right, you should stay.”

“ _Stay_ ,” Heather repeats, nodding. To stay with Bill is more than she could have hoped for, when she’d first gone to the forbidden lands to make the deal that steals her words, even now.

“If you like,” Bill replies, cheekily. There’s a smile at the corner of her mouth that Heather already adores.

Doctor Duodecim makes a noise of confusion, and quickly runs away to strike up an argument with Doctor Undecim, who happily complies. Heather just returns Bill’s smile, not paying attention to the bickering doctors.

 

~

 

Bill shows Heather to her room, running about in a tizzy, seemingly unsure as to how to proceed. Finally, Bill decides to fill a tin container with warm water, and explains, when Heather stares at it in confusion, that the contraption is a bathtub – intended for washing. Heather steps out of Bill’s coat, and Bill jumps, turning around quickly and stuttering out something about finding Heather some clothes.

Stepping into the tub, Heather discovers that the water is pleasantly warm against her skin, and softer than the seawater she’s lived in all her life. She shivers, and dunks her head below, but rises spluttering when it becomes clear that she can no longer breathe as she once did below the surface.

It confuses her, how this change can happen – she asked for legs, not necessarily humanity. But she has it nonetheless.

Bill returns not long after with clothes for Heather, chattering about the crew, and how excited they all are to meet her. Heather thinks about how she hadn’t even considered them – she’d only wanted to meet Bill, speak with her, understand her world through her eyes. Yet here she stands, wrapped up in a piece of cloth called a towel, with a new haphazard family claiming her as their own before even knowing her face. She wonders if that is a mark of humanity, or whether this group of humans is simply different.

 

~

 

That evening, Heather meets the crew that Bill has been excitedly speaking of all afternoon.

There are the Ponds – the pregnant Amy, insisting she does not need the arm of her husband, Rory, to stand and greet Heather with a grin and a brisk handshake. Then there’s Missy, whose glittering eyes spark with something a little darker than mischief as she greets Heather with a kiss on each cheek. Clara Oswald is next, stopping by on her way upstairs to meet with Doctor Duodecim on some matter or another – she greets Heather politely, but with an air of abstraction. Finally, Nardole rounds up the pack, exclaiming with delight to meet Heather, and quick to explain that the small crew is usually doubled in size, but while they are mired, Doctors Decim and Novem, Rose, Jack, Mickey, Donna, Martha, and the rest have decided to proceed further inland in search of more supplies. Heather’s brain spins with the sudden onslaught of names, and she quickly forgets at least half – but no one seems to mind, least of all Bill, who takes her aside after the food is served to speak quietly in a corner.

“Are you all right?” Bill asks, her brow furrowed.

“ _All right_ ,” Heather repeats, nodding.

Bill bites her lip, looking apologetic. “Just wanted to check in – I know the others are a rowdy lot, but they’re good people.”

“ _Good people_ ,” Heather says, with a smile.

“I wish I could – I wish we could talk more,” Bill sighs.

Heather looks down guiltily. She knew the price she was paying when she gave her voice to the echoes.

“Can you read?” Bill asks as if the thought has only just occurred to her.

Heather shakes her head. Merfolk have no script, and she cannot read human letters either.

“Would you mind if I taught you? I mean – could I teach you?”

Heather nods enthusiastically, trying to convey how much it means to her that Bill wishes to speak with her, to communicate.

Bill grins, an expression Heather is beginning to realise is her typical look. It is the kind of smile that transforms a whole face in friendship, and it sets something inside Heather to thrumming with shared joy.

“All right then,” Bill says. “While you’re here … I’ll teach you to read.”

 

~

 

Bill keeps to her promise. Each night, and sometimes for much of the day, too, when there is not much work to be done (surprisingly often), Bill sits with Heather, patiently teaching her letters, sounds, and signs to let them communicate. Heather finds herself smiling during her lessons – the diminutive thing she possesses that passes for a smile, anyway. And that is something she is eternally grateful for, because time outside her lessons passes impossibly slowly, evermore agonising with the constant thought in the back of Heather’s head that Bill does not love her, and without that love, her curse will never be dissolved.

That is perhaps unfair of her. Bill certainly likes her, is fond of her, even. They sleep in the same cabin. They spend time together. Bill smiles at her.

But Bill cannot love her. Without words to ease their souls together, there cannot be love. Heather understands her curse now. To have her legs, her throat must be stuck, preventing love’s growth. The echoes made her make a promise that would benefit them and them alone.

Heather should have known better.

There is no one to blame but herself, yet – still, on occasion, she finds herself taking out her anger on the others.

One evening, she watches Rory dutifully marching back and forth between their table in the inn and the kitchen, fetching things for his ever-more pregnant wife, while Amy laughs and kisses his forehead with the ease of affection that comes from many years together. It makes Heather’s heart ache with a cold, strange pain.

“Tell me, Rory, have you ever considered you’re getting the short end of the stick?” Amy says, giggling. He has just brought her a third serving of roasted potatoes.

“Never,” he says, voice impossibly gentle even as he looks away, as if it is nothing.

“You’re too good for me,” Amy whispers to him. Heather is not meant to hear.

Nor respond.

“ _Too good_ ,” she blurts out, unable to help herself.

Rory and Amy suddenly whirl around to stare at her, and Heather feels a flush creep up her neck.

That was cruel, she knows. But – they are so happy together.

Heather runs.

 

~

 

Bill finds her, because of course she does.

Heather turns her head away in shame. She is staring out at the ocean, feet (after all this time unfamiliar) just out of reach of the water. The sand is cool on her soles.

“Hey,” Bill says, softly. Everything about her is.

“ _Hey_ ,” Heather repeats, a concession. She tries not to repeat, most of the time. It is irritating, to never say what she means. Here, she means, _I’m sorry_.

“It’s all right. I forgive you,” Bill murmurs. Heather tries not to startle at how well Bill knows her thoughts. “And so will Amy, when she calms down. Giver her time.”

“ _Time_ ,” Heather sighs. Time. She has only a few scant months left.

“Feels like you only just got here, doesn’t it?”

Heather nods. She should have asked for longer than a year.

Bill nods slowly. “Yeah.”

Without warning, Bill’s head comes down to rest on Heather’s shoulder, hair tickling at her neck. Heather sits very, very still, waiting for the moment to break, for Bill to leave her be and give up on her.

But Bill does not. And they sit together in silence as the sun begins to set.

Heather’s heart races.

“Come back to my room. It’s going to be well freezing tonight,” Bill says, finally. “We could – if you want, we can share. All right?”

To share a bed, to be with Bill, to be warm when it is so difficult to feel anything at all above the water? _Of course. Yes. A thousand times, yes, yes_.

“ _All right_.”

They return to the inn. Heather writes out her apologies, to Amy and Rory alike. Bill slips them under the couple’s door, and Heather settles into Bill’s bed, wrapping herself in Bill’s sheets. She inhales quietly, and squeezes her eyes shut, pretending this intimacy means something it cannot.

Bill joins her within a few minutes, the chilly air letting in a draught as she climbs in. Heather shivers.

“Here,” Bill whispers, pulling her close.

Heather rests her head against Bill’s collar bone, pulling her hands tightly into herself, so as not to touch. She could not bear to touch.

Bill seems to hesitate too, before relaxing her muscles, one by one. The arm over Heather’s shoulder softens almost imperceptibly, and Bill’s breathing slowly evens out as the bed warms.

The last thing Heather thinks is to wonder at how such closeness can bely such a lack of attachment.

**Notes for the Chapter:**

> Sorry this is so late!! Working on a few different projects.


	3. Chapter 3

Time is drawing shut, like a terrible trap Heather cannot escape.

She watches over the crew with increasing agitation. Amy and Rory are so happy together it makes her feel sick, and the Doctors bicker and compete for the attention of Clara with practised familiarity. These things she can understand, these things she can put up with.

But Bill –

Bill has a flirtation that Heather cannot hope to compete with.

Penny, a woman from the village, is friendly enough to them all – if perplexed, as Heather once was, by their behaviour. Bill sees her beauty, though, and the iron that keeps Penny strong even as her parents warn her against association with the crew of the Tardis. It is only a matter of time before Bill falls in love with her. And it is only a matter of time until the crew rejoin their ship and sail away, while Heather sinks back into the ocean to become but another echo in the terrible vast plains.

The crew are all abuzz in these final weeks before setting sail once more. Heather watches them all silently, from the sidelines. No one pays her much mind, excepting Bill, but Heather is quick to push her away, not wanting her fate to play on Bill’s mind when the time inevitably comes for her to leave them.

But Bill, as always, has a way of surprising Heather.

“Heather,” she says softly, one night.

They are together are the edge of the ocean once more. Heather had intended to go out alone, of course, but Bill had joined her without a word. Some selfish part of Heather hadn’t let her push Bill away – hadn’t let her intention to make their separation easier overcome her desperate desire to be _seen_ by Bill.

Heather nods, to show Bill she’s heard, but doesn’t look away from the darkening sky over the oppressive sea. She needs to acclimatise herself to what is going to happen.

“I’ve been thinking,” Bill says, beginning slowly. “See, I know you know that the Tardis is nearly shipshape again. We’ve been preparing to leave for a few weeks now, finishing up business, calling back the rest of the crew from the country …”

Heather nods again.

Bill takes a breath.

“Well, I was wondering if – maybe, you don’t have to – if you would want to come with me when we leave. Us! Come with us, is what I meant.”

For a moment, Heather’s heart leaps. She turns her face towards Bill, trying to let her wonder speak through her eyes. Bill shifts awkwardly, seeming flustered.

“I mean – it’s not a big deal, we’ve got a few people joining us – there’s Penny, obviously –”

“ _Penny, obviously_ ,” Heather interrupts, quietly. For the thousandth time, she wishes she had the words for devastation – for heartbreak.

Bill nods, not noticing Heather’s distress.

“Yeah. I don’t want you to feel pressured, or anything – it’s all right if you … If you want to stay here, I just thought …” Bill trails off.

For a few minutes, they sit once more in silence, as Heather begs herself not to cry.

“Look,” Bill says, finally, “We’re casting off tomorrow to give her a bit of a test run before we set sail proper again. Will you come along? It’ll just be for a day.”

“ _Just for a day,_ ” Heather says softly, before nodding. Just for a day. She can pretend for that long.

She can have one day of happiness before she gives up hope entirely.

 

~

 

The next day dawns with sunshine on the horizon over the ocean, and a clear blue sky to match the sea. Everyone agrees that there could be no better day to take the Tardis on a pleasure cruise – and that, of course, is why a horrific wind blows in the second they are out beyond the bay.

Heather doesn’t need things explained to her. As a mermaid, she had known never to swim near the shoreline under any circumstances, but most especially during a storm, when the water is whipped into a frenzy and the currents take control of any fool unlucky enough to be within them.

Bill had taken her on board that morning chattering excitedly, giggling as Heather stumbled around, trying to find her “sea legs”. Heather hadn’t been able to point out the irony, but it was a bittersweet thing, to see Bill laugh. And then Bill had been called away, needed to climb some ropes or some such nonsense – Heather still doesn’t quite understand all the sailing business, despite her time with the crew.

She’s just looking for Bill, needing to warn her of what’s to come, when the crew begin to shout and hurry around the deck, above, in the ropes – everywhere. She knows they’ve sensed the danger at last, and comes to a halt, feeling a trickle of fear down her spine.

A figure slams into her, and she stumbles, reeling.

“Heather! Get below, I don’t like the look of those clouds!” Doctor Duodecim orders her, and before she can protest, she is bundled into his cabin.

Inside she paces for several agonising minutes. She stills, eventually, realising she will need to pay close attention to the feel of the ship in order to figure out what she must do. Closing her eyes, she slows her frantic breathing, and forces herself to focus on her surroundings.

The sea is far from calm, but she knew that already. Her feet are straining in her shoes, trying to keep her upright. The sound of the wind is long and low – angry, dangerous. They are still shouting outside, something about a stuck sail …

_Bill_.

She’s already fallen from the sails once.

Heather’s not going to let it happen again.

She takes a breath, and lets herself feel it all for just one more moment. How happy she’s been with these people … and how much she would give up for them.

And then she strides towards the door to the cabin, and forces it open against the howling wind. Outside, the noise is multiplied a thousandfold, and Heather struggles to draw breath. She can see the crew running about and still, still shouting uselessly at one another, trying to communicate what to do – but Heather has eyes only for Bill, the only one of them who is still stuck in the ratlines.

Bill’s hand is caught, and in her struggle to free herself, she’s veering wildly along with the loose ropes. If she gets herself untangled, she’s going to fall – it’s what happened the first time, when Heather saved her.

With a peculiar sense of calm, Heather realises that she is going to have to save her again.

She swallows.

Behind her, someone screams into the wind – she thinks she hears her name.

“COME BACK! HEATHER – BILL!”

“Bill,” she whispers to herself, unheard.

She doesn’t let herself think.

She just runs – to the side of the ship, where the railing is lowest – where there’ll be nothing to stop her –

And she jumps.

The water is colder than she remembered it. She gasps on instinct, having lost her gills, and the flood of icy water that fills her throat makes her choke. But before she can lose her senses, she cries out, with everything inside her –

_Let me save her. Ocean, mother of us all – let me save her!_

There is a breathtaking moment of stillness. Faintly, Heather thinks she can hear the echoes wailing.

A burst of light blinds her, and the noise comes rushing back. She opens her eyes and her throat to scream, but the pain is over in a flash – and she can breathe again.

She looks down, and sees a familiar but nearly forgotten sight: her tail, pale gold and shimmering, and stronger than her legs have ever been. At her neck, her gills move silently, letting her breathe once more. The salt no longer stings her eyes.

A faint splash awakens her from her stupor, and she turns about blindly, looking for the source of the sound. It doesn’t take her long to spot the figure struggling in the water nearby, and she swims towards it quickly, praying that she’ll get there in time.

Relief and horror mix within her when she realises it’s Bill. Bill is still struggling, which is a good sign – but it will make what Heather’s going to have to do next more complicated.

She swims up to Bill, whose eyes are screwed shut in the sting of salt. Heather moves in swiftly, putting a hand on either side of her face, and Bill suddenly stops moving. Her pulse jumps under Heather’s pinky. She opens her eyes, squinting, seeking out her saviour. Without thinking, Heather leans in and kisses her, just to reassure her – to show her she’s safe. That Heather won’t let her drown.

Heather takes Bill’s hands and pulls her upwards, swimming with all the grace she never mastered on land.

They burst through the surface of the water, Heather breathing clear air into her lungs, while her gills ripple in the cold. Above, the sea is – impossibly, miraculously calm. Heather doesn’t have time to wonder at it though, limp as Bill is in her arms. She pulls Bill in close to her body, and watches worriedly as Bill opens her eyes, seeming to hardly believe it when she coughs, and can drawn in the cold air with a shudder. She blinks owlishly, looking around, before her eyes land on Heather’s face.

“Heather,” she breathes, confused.

“Bill,” Heather replies, smiling with relief.

Bill’s eyes widen even further.

“Did – did you – am I hallucinating, or did you just speak?” Bill stutters.

“You are not hallucinating,” Heather laughs, despite herself.

“Oh,” Bill says, mother gaping like a fish. “Well. Yes. Right. What – what happened?”

“I knew you would fall when you freed yourself,” Heather explains. “I jumped before you. So I would be ready for you.”

For the first time, Bill seems to realise that Heather’s holding her up, and she freezes.

“Relax, Bill,” Heather says. “It makes it easier to lift you. I am stronger than you are in the water, you know.”

Bill looks down, and stares – and stares, and stares.

“You … you’re a … you’ve got …”

“Yes,” Heather says, trying not to sound as mournful as she feels. There’s no chance Bill will be able to forgive her for lying about this … and no chance, now, for them to be together …

“Bloody hell, I always told mum I’d fall in love with a mermaid, but I never thought it’d actually happen!”

Heather drops her.

She swears as Bill slips back into the water, and swiftly dives back under to pull her up again.

“I am sorry – so sorry! Bill, are you all right?”

Sputtering, Bills nods.

“Sorry,” she chokes out, and Heather might be imagining it, but some of the warmth looks like it is returning to her cheeks.

“Did you say …”

Bill groans. “Ugh, yeah. I did. I never meant for you to find out like that.”

“I am glad,” Heather says. “All this time – I could never say it. I did it for you.”

Bill stares at her in amazement.

“Why?”

“I saved you once before. I wanted … I wanted to see you again. I asked the echoes, and they gave me legs, but they took my voice … There is always a price, with the echoes.”

“You did that because you wanted to see me?”

“I was always curious about the world above. But you made me want it more. You made me brave.”

“But – you’ve got a tail again.”

Heather nods, looking away from Bill’s questioning gaze. “I asked the ocean to let me save you, and it did. But I think … my voice was a condition of –”

“What?”

“Love,” Heather admits, blushing. “They said I could be human forever, could have my voice back, if I kissed the one who loved me.”

“Oh,” Bill says, and they are both silent for a moment.

“Heather?”

“Yes?”

“What happened to the storm?”

Heather blinks, having forgotten about it entirely.

“I – I do not know.” But an idea occurs to her that makes her shiver. “Maybe … when I asked the ocean to let me save you …?”

“BILL POTTS, AS I LIVE AND BREATHE!”

They both jump, and Heather nearly drops Bill again, as a voice from afar cries out. They turn to see the Tardis, a little battered but mostly unharmed, sailing towards them, the crew cheering at the sight of them. Bill smiles with relief, but Heather’s stomach turns uneasily.

“Will you let me aboard?” she asks, nervously. “Just so that I know you are safe.”

“Of course – of course! Will it be safe? Can you breathe?”

“Yes, for some time. I will be all right.”

“All right,” Bill says quietly, but there’s a worried look in her eyes that Heather cannot reassure her of.

 

~

 

The crew, to put it lightly, are gobsmacked to learn the truth of Heather’s origins. The Doctors shout at her, each other, and everybody else, until Amy shuts them up and Clara drags Doctor Duodecim out by his ear. Heather watches these proceedings from a chair that Rory is gracious enough to lower her into, given that she no longer has legs of her own to stand on.

Hours pass as they debate what to do – they cannot return to land with Heather in tow, but she is adamant that she will not leave without knowing Bill is safe and unharmed. The Doctors examine Bill, eventually (they must cease arguing first,) and pronounce her in need of warmth and food. The sea is calm, though, so it is finally decided that they ought to stay put for now.

Grateful, Heather asks to be taken to Bill’s room. After reassuring everybody several times that she will call for help when she needs it, and that yes, she really will be all right to breathe for a few more hours yet, they take her down, and mercifully leave her alone with Bill.

“Get in here,” Bill says sleepily from her bed.

Heather starts. “I thought you were asleep.”

“Will be soon. Come to bed.”

Heather smiles.

It takes some manoeuvring, but they left her very near the bed, and so she manages to lift herself from the chair and use the weight of her tail to push herself into the covers.

“Stay with me,” Bill mumbles.

Without a way to survive above the surface, Heather can’t make that promise. She says nothing, and eventually, exhausted by the events of the day, wrapped inside Bill’s arms, she falls asleep.

When she wakes up, she knows in an instant that something has changed. The mild fatigue of being out of the ocean and without use for her gills is gone, and the weight below her hips is lighter. Heather keeps her eyes closed for many minutes, fighting the urge to open them in case she’s dreaming.

But open them she does. And she lets out a strangled noise that wakes up Bill beside her, who upon opening her eyes, gasps too. Because Heather’s legs have returned, by some _miracle_ –

_Of course_.

The same miracle the ocean granted her the first time.

“I think I understand it,” she blurts out. “When I am in the ocean – I am within it. And when I am above it – I am beyond it. Bill –”

“We can stay together.”

Heather turns to see Bill’s face, and her eyes, shining with unshed tears.

“We can stay together,” she repeats, and this time, it is with the all the joy she has long since dreamt of, knowing that her heart’s desire has been granted without conditions, for the sake of love alone.

**Notes for the Chapter:**

> Sorry this took forever to finish. I've been kinda bummed lately about the lack of feedback on ao3. You can see the kudos and hits go up and up and up without a single comment and it just makes you wanna give up. But here it is! The end! Hope you liked it.

**Author's Note:**

> [My Tumblr.](https://gallantrejoinder.tumblr.com/)


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